IEEE TSE 16, 11, November 1990
The Evolving Philosophers Problem:
Dynamic Change Management.
Jeff Kramer and Jeff Magee
ABSTRACT
One of the major challenges in the provision of distributed systems is the
accomodation of evolutionary change. This may involve modifications or extensions
to the system which were not envisaged at design time. Furthermore, in many
application domains there is a requirement that the system accomodate such change
dynamically, without stopping or disturbing the operation of those parts of the
system unaffected by the change. Since the description of software structure
(components and interconnections) provides a clear means for both system
comprehension and construction, it seems appropriate that changes should also be
specified as structural change, in terms of component creation/deletion and
connection/disconnection. These changes are then applied to the operational system
itself to produce the modified system.
This paper presents a model for dynamic change management which separates
structural concerns from component application concerns. This separation of
concerns permits the formulation of general structural rules for change at the
configuration level without the need to consider application state, and the
specification of application component actions without prior knowledge of the actual
structural changes which may be introduced. In addition, the changes can be applied
in such a way as to leave the modified system in a consistent state, and cause no
disturbance to the unaffected part of the operational system. The model is applied to
an example problem, "evolving philosophers". The principles described in this
model have been implemented and tested in the Conic environment for distributed
systems.
Department of Computing,
Imperial College of Science, Technology and Medicine,
180 Queen’s Gate,
London SW7 2BZ, UK.
Evolving Philosophers page 1 August 19, 1991